I for one understand what you're going through. I had a similar situation and ended up generating document which included everything and then manually removing unnecessary data.
I would like nothing more but to see RTF generator being "beefed" up with some conditional parameters (i.e. WHERE Element.Type="Actor") in place of tags so that certain information can be included based on the certain characteristics or properties of an element (I use element very loosely here to imply every tag in the document).
I had a lot of previous experience generating documentation out of Rational SODA and even though I didn't like it (very buggy and "sensitive') it had such functionality as specifying conditions prior to generating a document.
I know we can resort to programming (done that too) and get information out of EA using EA's automation interface but that's not that simple and not easily understandable by the average user.
Having said this, your only option is to resort to the suggestion from "ged" and use in your document a section where you can dump "Package->Diagram->Element" and then cut everything else from there but Actors. Another one is to use Connector->Source->Element with Element.FullName and Element.Type included. That way you can see which elements are of type of Actor and remove the other ones.
Unfortunately, as you can see manual workaround is required. I guess that's with every documentation we have to deal with - you kind of have to spend some time typing and formatting

Regards,
D